Most climate change predictions have only examined the next hundred years. But now a new, even more long-term model suggests that temperatures could rise as much as ten degrees Celsius by 2300 — creating conditions not seen for 34 million years.

This is one of four scenarios predicted by an international team of climate scientists, who have modeled the next 300 years of climate change based on various possible courses of action. By far the most dire scenario, this forecast only goes into effect if humans continue to burn fossil fuels into the 22nd century without any appreciable cuts in emissions.

If that happens, according to their forecast, atmospheric carbon dioxide levels would rise from their present, already worrisome, level of 338 parts per million to a whopping 2,000 parts per million. Such high levels would in turn raise global temperatures by as much as ten degrees Celsius, creating a global hothouse not seen since the Eocene epoch 34 million years ago.

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A general increase of ten degrees is dramatic enough, but the effects wouldn't be the same everywhere, with the polar regions seeing far greater increases than the tropics. In this scenario, Arctic ice would melt completely, and the far northern reaches of Canada, Russia, and Greenland could be covered in plants that are now only found in tropical or southern temperate regions, becoming lush forests like they were back in the Eocene.

Right now, it appears that the Antarctic ice is safe through the 23rd century, thanks to its isolation from the other continents, but there are still factors that this current model has not considered. In particular, the melting of the North Pole would release huge amounts of methane, itself a serious greenhouse gas that could accelerate southern melting. Plants and trees in the Arctic would also absorb more sunlight than the snow and ice currently does, and the model suggests that that could boost temperatures another three degrees.

Also, if we really did return to Eocene-like conditions, there's the question of whether the oceans could still store their share of carbon - based on sample analysis from that epoch, carbon levels were very low back then, which would suggests more of the gas escaped to wreak havoc in the atmosphere.

Of course, this is a worst case scenario, and it's one of the more preventable outcomes of the current climate change. But it's a stark reminder of how much power we have to shape and transform our planet, unleashing conditions unknown for 34 million years... even if we don't actually want to.